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Supercritical fluids as solvents for enzymatic reactions
Maja Leitgeb, Mateja Primožič, Željko Knez, 2007, pregledni znanstveni članek

Opis: Enzymes may act in different solvent systems. Water as the solvent in vivo may be replaced partially or mostly with other solvents, such as micro-emulsions, organic solvents, reversed micelles, ionic liquids and supercritical fluids (SCFs).Several types of enzymatic reactions were performed in SCFs. Influence of SCFs on enzyme stability and activity is presented on different examples; on different reaction systems (hydrolysis, transesterification...) and on the use of non-immobilized (Subtilisin carlsberg, Aspergillus niger...) as well as immobilized enzymes. Several types of high-pressure enzymatic reactors (batch-, stirred-tank-, extractive semibatch-, recirculating batch-, semicontinuous flow-, continuous packed-bed-, and continuous-membrane reactors) have been used for the performance of enzymatic reactions. In the studies on stability of biocatalysts in a high-pressure batch-stirred tank reactor changes in biocatalysts activity due to pressurization/depressurization steps were observed. Interesting alternative to overcome this inconvenience is the use of the high-pressure continuous membrane reactors, where just single compression and expansion step is necessary.
Ključne besede: enzymatic reactions, supercritical carbon dioxide, high-pressure, enzyme stability, high-pressure reactors
Objavljeno v DKUM: 31.05.2012; Ogledov: 3047; Prenosov: 143
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Proteinase-catalyzed hydrolysis of casein at atmospheric pressure and in supercritical media
Mateja Primožič, Maja Leitgeb, Željko Knez, 2006, izvirni znanstveni članek

Opis: In the presented work, reaction parameters for hydrolysis of casein, catalyzed by Carica papaya latex at atmospheric and high pressure, were optimized. Casein is a remarkably efficient nutrient, supplying not only essential amino acids, but also some carbohydrates, calcium, phosphorus and therefore is very important for the food industry. Different reaction parameters such as temperature, stirring rate, casein and enzyme concentration were studied to found the optimal conditions for the reaction. Reactions were performed at atmospheric pressure; an influence of temperature/pressure on the casein hydrolysis in supercritical carbon dioxide (SC CO2) was also investigated to improve the reaction rates. Higher conversions were achieved when the reactions were performed in SC CO2, even though casein was not soluble in this medium.
Ključne besede: chemical processing, high pressure technology, supercritical CO2, enzymatic reactions, proteinase, Carica papaya latex
Objavljeno v DKUM: 31.05.2012; Ogledov: 2006; Prenosov: 45
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